Ames and random amplified polymorphic DNA tests for the validation of the mutagenic and/or genotoxic potential of the drinking water disinfection by-products chloroform and bromoform.

Chloroform and Bromoform are two abundant trihalomethanes found in Algerian drinking water. The investigation of the mutagenic hazard of these disinfection by-products was studied by Ames test as prokaryotic bioassay to show their mutagenic effects. For this, Salmonella typhimurium TA98 and TA100 strains were employed. Both chloroform and bromoform showed a direct mutagenic effect since the number of revertant colonies gradually increase in dose-dependent manner with all concentrations tested with the two bacterial strains and these were both in the absence and presence of S9 metabolic activation. The genotoxic hazard was also studied by random amplified polymorphic DNA test on the root cells of Allium cepa as eukaryotic bioassay. DNA extracted from the roots of the onion were incubated at different concentrations of chloroform and bromoform and then amplified by polymerase chain reaction. This was based on demonstrating a major effect of disappearance of bands compared to roots incubated in the negative control (distilled water). The results showed that these two compounds affected genomic DNA by breaks although by mutations.

Genotoxicity of Thermopsis turcica on Allium cepa L. roots revealed by alkaline comet and random amplified polymorphic DNA assays.

This study was undertaken to evaluate genotoxic potential of Thermopsis turcica aqueous extracts on the roots of onion bulb (Allium cepa L.) by comet assay and random amplified polymorphic DNA technique. The Allium root growth inhibition test indicated that the EC50 and 2×EC50 values were 8 and 16 mg/ml concentrations of T. turcica aqueous extracts, respectively. The negative control (distilled water), positive control (methyl methane sulfonate, 10 mg/l) and 8 and 16 mg/ml concentrations of T. turcica extracts were introduced to the roots of onion bulbs for 24 and 96 h. The root growth, DNA damage in root cells and randomly amplified polymorphic DNA (RAPD) profiles of root tissue were used as endpoints of the genotoxicity. The comet assay clearly indicated that dose-dependent single strand DNA breaks in the root nuclei of onions were determined for the treatment concentrations of T. turcica extracts. In comparison to RAPD profile of negative control group, RAPD polymorphisms became evident as disappearance and/or appearance of RAPD bands in treated roots. The diagnostic and phenetic numerical analyses of RAPD profiles obviously indicated dose-dependent genotoxicity induced by Thermopsis extracts. In conclusion, the results clearly indicated that water extract of T. turcica has genotoxic potential on the roots of onion bulbs as shown by comet assay and RAPD technique.

Evaluation of 2,4-D and Dicamba genotoxicity in bean seedlings using comet and RAPD assays.

The present study was undertaken to evaluate genotoxic potential of two auxinic herbicides [2,4-dicholorophenoxy acetic acid (2,4-D) and 3,6-dichloro-2-methoxybenzoic acid (Dicamba)] in the roots of common bean (Phaseolus vulgaris L.) seedlings. Two-day-old etiolated seedlings were treated with 10 ppm methyl methanesulfonate (MMS, positive control) or 0.1, 0.2, or 0.3 ppm of either 2,4-D or Dicamba. At the end of a 96 h growth period, root growth, total soluble protein content, DNA damage in individual cells (comet assay scores) and randomly amplified polymorphic DNA (RAPD) profiles were used as endpoints of genotoxicity. 2,4-D and Dicamba were clearly dose-dependent root growth inhibitors. Total soluble protein content was significantly decreased in the positive control and at high concentrations (0.2 and 0.3 ppm) of Dicamba. Soluble protein content increased significantly only at 0.3 ppm 2,4-D (P<0.05). In the comet assay, DNA fragmentation increased in a dose-dependent manner. The diagnostic and phenetic analyzes of appeared and/or disappeared RAPD bands indicated that dose-dependent DNA polymorphism was induced by both herbicides. Genomic template stability was significantly affected at all 2,4-D and Dicamba doses tested. Overall 2,4-D and Dicamba have similar effects on DNA damage detected by comet and RAPD assays.

Toxic chemicals-induced genotoxicity detected by random amplified polymorphic DNA (RAPD) in bean (Phaseolus vulgaris L.) seedlings.

Assessment of genotoxins-induced DNA damage and mutations at molecular level is important in eco-genotoxicology. In this research, RAPD was used to detect DNA damage in the roots and leaves of bean (Phaseolus vulgaris L.) seedlings exposed to toxic chemicals of Hg, B, Cr and Zn (HgCl(2), H(3)BO(3), K(2)Cr(2)O(7) and ZnSO(4)7H(2)O) at concentrations of 150 and 350 ppm for 7 d. Inhibition of shoot and root growth and increase of Hg, B, Cr and Zn element contents in the roots and leaves were observed with an increase in the concentration. For the RAPD analyses, 12 RAPD primers of 60-70% GC content were found to produce unique polymorphic band profiles and subsequently were used to produce a total of 120 bands of 263-3125 bp in the roots and leaves of untreated and treated seedlings. Polymorphisms became evident as disappearance and/or appearance of DNA bands in 150 and 350 ppm treatments compared with untreated control treatments. The DNA changes in RAPD profiles were more in the roots than in the leaves. The highest polymorphism was observed in boric acid treatments among the toxic chemicals. In a dendrogram constructed based on genetic similarity coefficients, the treatments were grouped into three main clusters: (a) root-B-150 ppm treatment grouped alone, (b) root-350 ppm-Hg, B, Cr and Zn treatments clustered together, and (c) the others including untreated control treatments merged together. We concluded that DNA alterations detected by RAPD analysis offered a useful biomarker assay for the evaluation of genotoxic effects of Hg, B, Cr and Zn pollutions on plants.